The most posterior of the three principal regions of the brain. In mammals and birds the hindbrain is divided into a rostral metencephalon and a caudal myelencephalon. In zebrafish, with the exception of the cerebellum, the ventral remainder of the metencephalon can be separated only arbitrarily from the more caudal myelencephalic portion of the medulla oblongata and thus these are not distinguished here. From Neuroanatomy of the Zebrafish Brain.